The present invention is related to the detection of medical invasive tool bending when inserted in a body, to evaluate its shape. It is also related to enhancing the ultrasound echo of an invasive tool.
Imaging methods, such as ultrasound or CT are used to guide the insertion of surgical tools for diagnosis and therapy. For example, ultrasound imaging procedures are routinely performed in association with fetal monitoring and development, breast biopsy, other biopsies, aspirations and other intervention insertions.
Systems for performing guided medical invasive procedures are disclosed for example, in the commonly assigned U.S. Pat. No, 5,647,373 (Paltieli); and PCT Applications; PCT/IL96/00050 (WO 97/03609), entitled: Free-Hand Aiming Of A Needle Guide; and PCT/IL98/00578, entitled: System And Method For Guiding Movements Of A Device To A Target Particularly For Medical Applications, all tree documents being incorporated by reference in their entirety herein.
In these systems a medical invasive tool is guided to a target on a body viewed by a medical imaging device, such as an ultrasound, CT, MRI, etc. The guidance is based on the measurement produced by a position measuring system comprising position measuring components and/or articulated arms attached at known positions to the medical invasive tool and to the medical tool. If the medical invasive tool bends during its insertion its calculated position and trajectory may become incorrect. This may arise if the position measuring component(s) is (are) attached at a relatively far distance from the tip of the medical invasive tool. Placing the position sensor on the tip of the invasive tool may eliminate the problem. However, this generally requires dedicated tools and in most cases, still introduces errors regarding the expected trajectory of the tool.
Knowing the expected position and velocity of the invasive tool can also be used for enhancing the ultrasound echo of the invasive tool by applying image processing tools on the originally produced image.
U.S. Pat. No. 4,429,539 (Vilkomerson) presented a method and an apparatus for detecting the position of a needle under ultrasound by placing a transducer element on the skin and on the needle tip being cooperative.
U.S. Pat. No. 4,407,294 (Vilkomerson) presented a method and an apparatus for detecting the position of a needle tip under ultrasound comprising two ultrasound detectors on the needle, viewable when in the vicinity of the ultrasound beam. U.S. Pat. No. 5,095,910 (Powers) presented a method and an apparatus for detecting the needle tip under ultrasound comprising a movable part in the needle tip that elicits Doppler.
These methods enable the operator to position the needle tip when viewed by the scanning plane of an ultrasound device. However, they exhibit drawbacks in that they require dedicated tools. Additionally, these methods and apparatus for performing these methods cannot provide information about the amount of bending of the needle. Also, the method disclosed by Powers (""910) is compatible for Doppler ultrasound only.
The present invention improves the contemporary art by providing computer controlled method and apparatus for detecting the bending of a medical invasive tool during its insertion in a body. The present invention also discloses methods and apparatus that compensate for such bending if it occurs, and are useful for example in interventions under ultrasound, CT or MRI.
The present invention also provides methods and apparatus for enhancing the ultrasound echo of an invasive tool, therefore improving the quality of the ultrasound image.
The term xe2x80x9cneedlexe2x80x9d is used herein to describe any invasive medical instrument or tool that is employed in a medical intervention. The term xe2x80x9cpositionxe2x80x9d will be used herein to describe location and/or orientation.
The term xe2x80x9cposition measuring systemxe2x80x9d is used herein to describe any system (magnetic, optic, acoustic, inertial, mechanical or any combinations thereof) that can be used in order to track the position of a body with respect to a reference position or with respect to another body in space. The term position measuring component is used to describe a component of a position measuring system, such as electro-magnetic/acoustic/optic transitter or receiver, reflector or other optic indicia, gyro or encoder, or any other component that enables the measurement of a body/set of coordinates with respect to another body/set of coordinates in space.
One embodiment of the apparatus of the present invention is semi-automatic, in that it requires the operator to maneuver the scanning head and/or the needle such as the scanning head views at least a portion of the needle or at least one point on the needle. The calculation of the expected needle position with respect to the scanning head and scanning beam is fully automatic, whereas recognizing the actual position of at least a portion of the needle on the image displayed by the medical scanning device may be automatic or manual.
The system comprises a medical imaging device, such as an ultrasound, a position measuring system comprising a position controller and position measuring components and/or articulated arms being attached to the needle and to the scanning head of the medical imaging device a data-processor, and an optional image processor. Additionally, the system comprises a display on which the operator can view the image produced by the imaging device and/or information regarding the position of the needle, and the amount of needle bending during insertion
A first position measuring component is attached at a known position with respect to the needle and a second position measuring component is attached on the ultrasound transducer. The relative position between the first and second measuring component is measured by the position measuring system. The second position measuring component is calibrated to the ultrasound transducer such that the position of the scanning plane of the ultrasound is known with respect to the second position measuring component. The expected position of the needle with respect to the scanning plane/volume of the medical imaging device may then be calculated based on the measurements and calibration above. Alternately, the needle and/or the ultrasound transducer are placed on articulated arms enabling to measure their relative position by mechanical means (encoders).
The needle is aimed at a target in a body or body volume viewed by an ultrasound imaging system. If the needle is thin, it may bend during insertion. The transducer may then be maneuvered such as to view at least a portion of the needle or at least one point on the needle. Points and portions on the needle may be identified by automatically or semi-automatically procedures according to the ultrasound echo of the needle. The information received from the position measuring system (position and movement parameters) together with actual points detected from the ultrasound echo enables the evaluation of the shape of the needle, and particularly, needle bending.
Knowing the position and velocity of the needle is also used for enhancing the needle echo in an ultrasound image or set of images. Points on the needle are searched in the ultrasound image or set of ultrasound images, respectively, according to the expected position and velocity of the needle. Applying standard image processing tools such as interpolation functions and local sharpening filters enables them to enhance the complete needle echo based on the recognized point(s).
The current invention can improve the performance of medical guiding systems for medical intervention, such as for example, the guiding systems presented in commonly assigned U.S. Pat. No. 5,647,373 (Paltieli), PCT/IL96/00050 (WO 97/03609), entitled: Free-Hand Aiming Of A Needle Guide, and PCT/IL98/00578, entitled: System And Method For Guiding Movements Of A Device To A Target Particularly For Medical Applications, all three documents being incorporated by reference in their entirety herein, or other existing guiding systems. The improvement is particularly important in applications where the medical invasive tool is thin and the position measuring component attached to the needle is not on the tip of the needle.